1. Field of the Invention
The present invention relates to a two-stage rotary compressor (hereinafter, simply “rotary compressor”).
2. Description of the Related Art
An existing rotary compressor includes, inside a cylindrical compressor housing that is a sealed container, a low-stage compressing section, a high-stage compressing section, and a motor that drives the low-stage compressing section and the high-stage compressing section. Further, the rotary compressor includes an accumulator on an outer side of the compressor housing.
A first communication hole, a second communication hole, and a third communication hole are separately arranged on a straight line along a central axial direction in an outer peripheral wall of the cylindrical compressor housing. One end of a low-stage suction pipe, which sucks a low-pressure gas refrigerant Ps that is inside the accumulator, is connected to a suction hole of the low-stage compressing section via the second communication hole.
Further, one end of a low-stage discharge pipe, which discharges a low-stage discharge gas refrigerant Pm outside the compressor housing, is connected to a discharge hole of the low-stage compressing section via the first communication hole. One end of a high-stage suction pipe, which sucks the low-stage discharge gas refrigerant Pm, is connected to a suction hole of the high-stage compressing section via the third communication hole. The other end of the low-stage suction pipe and the accumulator are connected by a low-pressure connecting pipe. The other end of the low-stage discharge pipe and the high-stage suction pipe are connected by an intermediate connecting pipe.
A flow of a gas refrigerant due to the pipe connections mentioned earlier is explained next. The low-pressure gas refrigerant Ps is sucked from the accumulator and passes through the low-pressure connecting pipe and the low-stage suction pipe. Next, the low pressure gas refrigerant Ps is sucked inside the low-stage compressing section due to the suction hole of the low-stage compressing section and compressed to an intermediate pressure, thus becoming the low-stage discharge gas refrigerant Pm.
The low-stage discharge gas refrigerant Pm, which is of the intermediate pressure that is discharged in a low-stage discharge space, passes through the low-stage discharge pipe, the intermediate connecting pipe, and the high-stage suction pipe. Next, the low-stage discharge gas refrigerant Pm is sucked inside the high-stage compressing section from the suction hole of the high-stage compressing section, and compressed to a high pressure, thus becoming a high-stage discharge gas refrigerant Pd. The high-stage discharge gas refrigerant Pd is discharged in an internal space of the compressor housing, passes through a gap of the motor, and is discharged to a refrigerating cycle from a discharge pipe. A conventional technology has been disclosed, for example, in Japanese Patent Application Laid-open No. 2006-152931.
However, in the conventional technology mentioned earlier, because the first communication hole, the second communication hole, and the third communication hole are separately arranged in a straight line along the central axial direction in the outer peripheral wall of the cylindrical compressor housing, for avoiding interference of the circular arc shaped intermediate connecting pipe that connects the low-stage discharge pipe and the high-stage suction pipe, the low-pressure connecting pipe that connects the low-stage suction pipe and the accumulator is three dimensionally bent at a right angle at two points, thus resulting in a complex shape. Due to this, a pipeline resistance increases and a pressure loss of a refrigerant increases, thus worsening compression efficiency of the rotary compressor.
Further, because a distance between the respective communication holes of the compressor housing is short, a pressure resistance of the compressor housing decreases. Moreover, a welding (brazing) operation of the low-pressure connecting pipe and the low-stage suction pipe becomes difficult. Similarly, a welding (brazing) operation of the intermediate connecting pipe with the low-stage discharge pipe and the high-stage discharge pipe becomes difficult.